16Bit can not display

[qtsun]

I found that cog-explorer can not display 16bit images ,it displayed black image

[constantinius]

Hi @qtsun, thanks for reporting the issue!
Can you provide a URL for the image, so I can check this?

[qtsun]

Hi @qtsun, thanks for reporting the issue!
Can you provide a URL for the image, so I can check this?

16bit images url
http://120.25.126.226:3000/LC8/qb_blouler_msi.tif
and Here is a 32bit single band image url
http://120.25.126.226:3000/LC8/test32bitSingleband.tif
Thanks for your reply !

[constantinius]

Unfortunately I cannot load your files as they don't support HTTPS. Maybe you can put them somewhere where HTTPS is enabled?

Also, when I open them via GDAL I get the following error:

$ gdalinfo /vsicurl/http://120.25.126.226:3000/LC8/qb_blouler_msi.tif
Warning 1: TIFFReadDirectory:Sum of Photometric type-related color channels and ExtraSamples doesn't match SamplesPerPixel. Defining non-color channels as ExtraSamples.

This might be a hint why nothing is visible

[tushar10sh]

@qtsun You have to change the the getMaxValue function inside of webglrender.js and max value in toMathArray function inside of renderutils.js. The max value present by default is 65535. For 16 bit files with low dynamic range, scaling with 65535 will cause the image to appear black. Just change the max value in these two files to the approximate max value of the tiff files you are working with; and build the package with "npm run build".
@constantinius There is no issue with http/https . I have tried with both protocols and it works.

[constantinius]

Regarding HTTPS I'm not so sure:

ERROR 11: CURL error: Failed to connect to 120.25.126.226 port 3000: Connection refused
gdalinfo failed - unable to open '/vsicurl/https://120.25.126.226:3000/LC8/qb_blouler_msi.tif'.

Yes, the default stretch used is to Uint16 max for Uint16 images. I have not yet implemented linear scaling, but it should be fairly easy to do.

[lnicola]

Hi! I have a different issue with 16-bit images:

This is after updating the renderer to return 4095 (a reasonable value for my TIFF) as the max value.

Sample file: https://nas.dend.ro/browse/public/cog.tif.

Scaling the image to 8-bit makes it show fine:

[constantinius]

Hi @lnicola

Thanks for the update. Unfortunately I cannot bring the image you provided to load. Could you maybe set CORS headers for it?

[lnicola]

@constantinius sorry for the CORS issue, but it's not easy for me to set up the headers correctly (to handle OPTIONS, actually). You might need to download it locally.